Accessory devices to improve wireless power transfer efficiency

Abstract

An accessory for improving wireless power transfer efficiency in a wireless power transfer system can include a magnetic (e.g., ferrite) core dimensioned and positioned so as to reduce flux coupling from the PTx winding into friendly metal of the PRx and/or to enhance flux coupling from the PTx winding to the PRx winding. The core may define an aperture corresponding to an outer dimension (e.g., outer diameter) of the PRx winding. The core may further have an outer dimension selected to intercept sufficient flux to reduce flux coupling into the friendly metal of the PRx, such as an outer dimension corresponding to an outer dimension (e.g., outer diameter) of the PTx winding. The accessory may be a case for the PRx device or may be configured to be affixed to the face of the PTx device and may also include one or more alignment fixtures.

What is claimed is: 
     
       1. An accessory configured to improve wireless power transfer efficiency between an electronic device and a wireless charger, wherein a wireless charging winding of the device and a wireless charging winding of the wireless charger are dimensionally mismatched, the accessory comprising:
 one or more alignment magnets that align and secure the accessory with respect to one or more alignment magnets in the electronic device; and 
 a core formed from a ferromagnetic material, the core being dimensioned and positioned so as to:
 reduce flux coupling from the wireless charging winding of the charger into friendly metal of the electronic device, the friendly metal including the one or more alignment magnets of the electronic device; and 
 enhance flux coupling from the wireless charging winding of the wireless charger into the wireless charging winding of the electronic device. 
 
 
     
     
       2. The accessory of  claim 1  wherein the one or more alignment magnets further align or secure the accessory with respect to the wireless charger. 
     
     
       3. The accessory of  claim 1  wherein the one or more alignment magnets form a ring. 
     
     
       4. The accessory of  claim 1  wherein the core is a ferrite core. 
     
     
       5. The accessory of  claim 1  wherein the dimensional mismatch comprises the wireless charging winding of the wireless charger being larger than the wireless charging winding of the electronic device and wherein the core defines an aperture corresponding to an outer dimension of the wireless charging winding of the electronic device. 
     
     
       6. The accessory of  claim 5  wherein the core has an outer dimension selected to intercept sufficient flux to reduce flux coupling into the friendly metal of the electronic device. 
     
     
       7. The accessory of  claim 6  wherein the aperture has an inner diameter corresponding to an outer diameter of the wireless charging winding of the wireless charger. 
     
     
       8. The accessory of  claim 1  wherein the accessory is a case for the electronic device. 
     
     
       9. The accessory of  claim 1  wherein the accessory is a shim configured to be disposed between the device and the wireless charger. 
     
     
       10. An accessory configured to be affixed to the face of a wireless power transmitter to improve wireless power transfer efficiency between an electronic device and the wireless power transmitter, wherein a wireless charging winding of the electronic device and a wireless charging winding of the wireless power transmitter are dimensionally mismatched, the accessory comprising:
 a core formed from a ferromagnetic material, the core being dimensioned and positioned so as to:
 reduce flux coupling from the wireless charging winding of the wireless power transmitter into friendly metal of the electronic device including one or more alignment magnets of the electronic device; and 
 enhance flux coupling from the wireless charging winding of the wireless power transmitter into the wireless charging winding of the electronic device; and 
 
 one or more alignment magnets that align and secure the accessory with respect to the electronic device. 
 
     
     
       11. The accessory of  claim 10  wherein the core is ferrite ring dimensioned to shield the metal of the electronic device from flux induced by at least one wireless charging winding of the wireless power transmitter. 
     
     
       12. The accessory of  claim 11  wherein the ferrite ring comprises one or more tabs sized and dimensioned to be positioned near one or more wireless charging windings of the wireless power transmitter to provide a desired level of shielding or flux redirection. 
     
     
       13. The accessory of  claim 11  wherein the ferrite core further comprises additional ferrite bars sized and dimensioned to be positioned near one or more wireless charging windings of the wireless power transmitter to provide a desired level of shielding or flux redirection. 
     
     
       14. An accessory configured to improve wireless power transfer efficiency between an electronic device and a wireless charger, wherein a wireless charging winding of the electronic device and a wireless charging winding of the wireless charger are dimensionally mismatched, the accessory comprising:
 one or more alignment magnets that align and secure the accessory with respect to one or more alignment magnets in the wireless charger; and 
 a core formed from a ferromagnetic material, the core being dimensioned and positioned so as to:
 reduce flux coupling from the wireless charging winding of the wireless charger into friendly metal of the electronic device, the friendly metal including the one or more alignment magnets of the electronic device; and 
 enhance flux coupling from the wireless charging winding of the wireless charger into the wireless charging winding of the electronic device. 
 
 
     
     
       15. The accessory of  claim 14  wherein the one or more alignment magnets further align and secure the accessory with respect to the electronic device. 
     
     
       16. The accessory of  claim 14  wherein the one or more magnets form a ring. 
     
     
       17. The accessory of  claim 14  wherein the core is a ferrite core. 
     
     
       18. The accessory of  claim 14  wherein the dimensional mismatch comprises the wireless charging winding of the wireless charger being larger than the wireless charging winding of the electronic device and wherein the core defines an aperture corresponding to an outer dimension of the wireless charging winding of the electronic device. 
     
     
       19. The accessory of  claim 18  wherein the core has an outer dimension selected to intercept sufficient flux to reduce flux coupling into friendly metal of the electronic device. 
     
     
       20. The accessory of  claim 19  wherein the aperture has an inner diameter corresponding to an outer diameter of the wireless charging winding of the wireless charger. 
     
     
       21. The accessory of  claim 14  wherein the accessory is a case for the wireless charger. 
     
     
       22. The accessory of  claim 14  wherein the accessory is a shim configured to be disposed between the electronic device and the wireless charger. 
     
     
       23. An accessory configured to be affixed to the face of a wireless power transmitter to improve wireless power transfer efficiency between an electronic device and the wireless power transmitter, wherein a wireless charging winding of the electronic device and a wireless charging winding of the wireless power transmitter are dimensionally mismatched, the accessory comprising:
 a core formed from a ferromagnetic material, the core being dimensioned and positioned so as to:
 reduce flux coupling from the wireless charging winding of the wireless power transmitter into friendly metal of the electronic device, the friendly metal including one or more alignment magnets of the electronic device; and 
 enhance flux coupling from the wireless charging winding of the wireless power transmitter into the wireless charging winding of the electronic device; and 
 
 one or more alignment magnets that align and secure the accessory with respect to the face of the wireless power transmitter. 
 
     
     
       24. The accessory of  claim 23  the core is ferrite ring dimensioned to shield friendly metal and alignment magnets of the electronic device from flux induced by at least one wireless charging winding of the wireless power transmitter. 
     
     
       25. The accessory of  claim 24  wherein the ferrite ring comprises one or more tabs sized and dimensioned to be positioned near one or more wireless charging windings of the wireless power transmitter to provide at least one of shielding or flux redirection. 
     
     
       26. The accessory of  claim 24  wherein the core further comprises additional ferrite bars sized and dimensioned to be positioned near one or more wireless charging windings of the wireless power transmitter to provide at least one of shielding or flux redirection.